A traveling-wire electroerosion machine commonly makes use of a continuous electrode wire stored in a wire storage means. The term "wire" is commonly used in the art and hence will be used herein as well to refer to a metallic or other conductive wire, ribbon, filament or tape designed to constitute a continuous traveling tool electrode in the electroerosion cutting system. The electrode wire is mounted on the machine so as to extend continuously between the wire storage means and a wire takeup means through a cutting zone along a predetermined path of wire travel. A wire traction means is commonly provided to continuously draw or pull the electrode wire out of the wire storage means and thus to continuously feed it to travel through the cutting zone and eventually to be collected onto the wire takeup means for disposal. A wire braking means is also provided to maintain taut the electrode wire traveling between the wire storage means and the wire takeup means along the path.
A workpiece is disposed in the cutting zone so as to be traversed by the traveling electrode wire. A machining fluid, typically distilled water, is supplied to the cutting zone while electrical machining current is passed between the traveling electrode wire and the workpiece to electroerosively remove material from the workpiece. As material removal continues, the workpiece is displaced relative to the traveling electrode wire generally transversely thereto along a predetermined cutting path to form a desired cut in the workpiece.
The electrode wire for use with an electroerosion cutting machine as described is commercially available in the form of a supply of the wire having a given length which is, say, wound on a reel. The wire is progressively unwound and consumed as cutting proceeds in a given electroerosion cutting operation. It is convenient and indeed desirable if the machine operator can be made aware of the amount of the electrode wire remaining on the reel at given time, or at each instant of time while the cutting is being carried out. Alternatively, the operator would desirably be advised of the noticed of the time period of cutting period available before the amount of the electrode wire remaining on the reel at such instant is used up.
It has been recognized that notice of such period cannot be given simply because the amount or the cutting period remaining cannot accurately be determined from the cutting period which has elapsed up to each instant during a given cutting operation. In general, in the traveling-wire electroerosion cutting process the rate of travel of the electrode wire or of with drawing the wire from the reel is caused to vary controlledly according to varying conditions in the cutting zone and also to the varying thickness of the workpiece traversed by the traveling electrode wire.